Cargo is typically transported in containers (“Unit Load Devices”), which are stowed in cargo holds either below the deck of passenger aircraft or below and above the deck in transport aircraft. The size and shape of Unit Load Devices vary depending upon the type of aircraft in use. For example, a very common type of aircraft container is the LD3 Unit Load Device, which has an added chamber at one end to conform to the curved sidewalls of the cargo hold compartments of either Boeing 747 aircraft, McDonnell Douglas DC10 aircraft, or similar aircraft. In each of these aircraft, the fuselage is round or oval in cross-section. In all aircraft, the gross weight of the airplane is a substantial factor, because of the cost of fuel. Even a slight reduction in weight is significant. As a result, many aircraft are utilizing fiber reinforced plastic panels. Further, containers for aircraft cargo are also now being formed of composites, in addition to the standard aluminum.
For many years, air cargo containers were made of aluminum alloy. Such containers are roughly handled and easily damaged when loaded into or unloaded from aircraft, and many problems therefore occur with such aluminum alloy containers. Aluminum containers have various disadvantages, such as conducting heat, condensation, and others. As a result, the use of composite panels has grown substantially.
Further, there has long been a concern in air cargo containers and pallets related to losses that may occur as a result of fire. Although aluminum does not burn, it does melt in the presence of temperatures exceeding 1200° F. and ceases to act as a flame barrier. In order to solve this problem in the past, there have been several approaches. One is to use thermal blankets, which will serve to suppress fire. Another is to utilize “active” flame suppression systems in the holds of cargo aircraft that have a heat sensor that can detect an internal temperature rise associated with fire. A nozzle then punctures the roof of a container and injects fire suppression foam. While both of these solutions have proven to work to a certain extent, they are relatively expensive and there are significant problems remaining.